1. Field of the Invention
This invention relates to a sheet stacking machine, whereby sheets or signatures can be stacked which are fed continuously as signatures and/or single or overlapping sheets.
2. Description of the Prior Art
Known in the art is a stacking machine of that general type, wherein to an entraining roller, partially encircled suitable conveying belts, is associated a series of further conveying belts which are mounted idle and driven by frictional engagement of the sheets or signatures being fed with the belts around the rotatively driven roller and related idle travelling belts.
The shortcoming of this prior art device is that the friction force between the sheets and idle-mounted belts is not always sufficient to ensure correct operation of the stacking machine, where it may happen that the sheets and/or signatures to be stacked--owing to this very conveying fault--jam the conveying belt means, thus requiring that the machine be stopped to free the latter of the sheets and/or signatures jammed in the conveying means.
An attempt has been made at driving also the outer belts facing the conveying belts over the rotating roller, but this involves difficulties hitherto unobviated, because owing to the variable thickness dimension of the overlapping signatures and/or sheets, there occurs a differential of peripheral speed between the belts linked to the driven conveying roller and the set of outer belts cooperating with the ones on the rotating roller.